The Treasury Department auctioned $25 billion in three-month bills at a discount rate of 0.035 per cent, unchanged from last week. Another $23 billion in six-month bills was auctioned at a discount rate of 0.060 per cent, up from 0.055 per cent last week.

The three-month rate was the highest since three-month bills averaged 0.045 per cent on March 31. The six-month rate was the highest since those bills averaged 0.065 per cent also on March 31.

The discount rates reflect that the bills sell for less than face value. For a $10,000 bill, the three-month price was $9,999.12, while a six-month bill sold for $9,996.97. That would equal an annualized return of 0.035 per cent for the three-month bills and 0.061 per cent for the six-month bills.

Separately, the Federal Reserve said Monday that the average yield for one-year Treasury bills, a popular index for making changes in adjustable rate mortgages, was unchanged at 0.10 per cent.